class Solution(object):
    def isSubsequence(self, s, t):
        """
        :type s: str
        :type t: str
        :rtype: bool
        """
        if len(s)==0: return True
        i = 0
        for ch in t:
            if ch==s[i]:
                i+=1
                if i==len(s): return True
        return False